Above is a picture of an oak leaf plant fossil called Quercus simulata (Knowlton, 1898). This plant fossil dates to the Miocene Epoch (23.8-5.3 million years ago). It was found in the state of Washington, USA. While not listed, it possible this specimen is from the Latah Formation.
The fossil was on display in the Evolving Planet section of The Field Museum of Natural History in Chicago Illinois, USA as of August 2020. Accession number is P22229. They have a nice collection of plant fossils on display.
This type of leaf specimen was described by Frank Hall Knowlton (1860-1926) in the U. S. Geological Survey Eighteenth Annual Report., Part. 3, page 728, plate 101, figures. 3,4; plate. 102, figures 1, 2 1898 in the Payette formation of Idaho.
Knowlton later identified in the Latah formation of Washington in U. S. Geological Survey Prof. Paper 140, page 38, plate 22 figures 3, 4, 1926. See leaf image from figure 3 below.
Source A Revision of the Flora of the Latah Formation by Edward Wilber Berry.
